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For those of us who love dogs, using DNA tests to deconstruct our mongrel pooch’s mysterious heritage is appealing because we want to be able to answer the question, “What kind of dog is that?” Companies say that DNA-based diagnostic tests, which sell for about $60, can answer the question by comparing your dog’s DNA to over 100 of the most popular breeds. But are the tests accurate? I decided to find out.

Chance, a 10-year-old mixed-breed dog who has lived with me for six years, was my guinea pig. I tested his DNA using three different tests. In 2008, when I wrote the prequel to this article (read it online at thebark.com/dna), I had his ancestry tested with the Canine Heritage Breed Test. At that time, the company used 96 markers and tracked them to 38 breeds. A marker is a gene or DNA sequence on a chromosome that indicates “breedness.” The labs claim that the markers they use are 99 percent accurate.

In May 2012, when I began doing research for this follow-up article, I tested his DNA with the amplified Canine Heritage Breed Test again because it had been substantially improved to 400 markers and 120 popular breeds. I could have paid $25 to upgrade the 2008 test. But to be fair in my test-of-the-tests experiment, I submitted his cheek swab under a different name and without a photograph, just in case, as many people believe, the tests are a scam. In addition, I used the MARS Wisdom Panel Mixed Breed Identification Test. Mars looks at 321 markers and includes 185 breeds in its database.*

To analyze and compare the results fairly, I needed to find out if the tests were processed the same way, and I researched the history of the breeds identified in Chance’s ancestry.

Comparing the Tests
Each lab analyzes DNA the same way. Upon arrival, samples are logged, tracked and monitored. DNA is extracted from the cheek swab and isolated, and copies are made to ensure a sufficient amount for processing. The genetic material is then chemically enhanced and run through equipment that looks for markers in the dog’s DNA that match breed markers in the database.

If a primary parent breed can’t be identified in the DNA, the program will look for a secondary grandparent breed, and so on and so forth, until it eventually clusters with a distant breed (if there is one). If there are no purebred ancestors, remnant breeds will be sought.

To identify markers that characterize a breed, labs take samples from multiple thousands of individual dogs representative of more than a hundred breeds. However, those dogs differ from one laboratory to the next. Although their sample sizes are big enough to absorb minor differences, no two dogs are exactly alike. Plus, line-bred dogs can affect results. For example, Labrador Retrievers bred exclusively for hunting may be more like each other than they are like the breed.

Chance’s Results
In total, I tested Chance’s DNA three times. I used the Canine Heritage test twice, in 2008 and 2012, to find out if the expanded breed library would affect the results. (It did.) I also used Mars Veterinary’s Wisdom Panel**. Although results differed, cumulatively the tests indicate that Chance is a mix derived primarily from spitz dogs and large terriers, with a tablespoon of sight hound, teaspoon of herding dog, pinch of guard dog and smidgen of bird dog.